First described in the 16th Century by Italian anatomist Costanzo Varoli, the pons
consists of two parts: the tegmentum, which contains the reticular formation, and the
pontine nuclei. It connects the medulla with the cerebellum, while its thick ascending and
descending fibers, "gangly giants,"(1) reach from brain stem to
neocortex. Its name is derived from the Latin for "bridge."

The prehistory of
bridge-building may begin with humans swinging across chasms on vines. In the 16th
Century, Spanish invaders of South America reported seeing Peruvian suspension bridges
built from fibers "woven into cables of the thickness
of a man's body." How old the technology was by that time is not known. Besides being
triumphs of human ingenuity, bridges are places of imaginative
space. Were ancient bridges the result of pontine fibers dreamed by ancient
shaman/engineers?

The pons secretes a class of
neurotransmitters called the amines, the best described of which are norepinephaline and
serotonin, which serve to allow the higher brain to pontificate over the organism. During
REM (dream) sleep, these substances are drastically reduced, replaced by the cholinergic
neurotransmitters--secreted by another part of the pons--, especially acetycholine, a
chemical commonly found the junctions of muscles and nerves. While we dream,
acetycholine inhibits kinesthesis, except for the eyes. (REM is an acronym for Rapid Eye
Movement.) The function of such eye-movement seems announce the passive viewing of images.

Michel Jouvet, who
pioneered research into the neurobiology of dreams, calls REM sleep
"paradoxical," because, although the cerebral cortex is flooded with images, it
cannot link them to the body, which is atonic. Jouvet calls dreaming a third state,
"a new formof an age-old concept--that of the
Upanishads of Hindu mythology--according to which the
human brain alternates between waking, sleeping without dreams, and sleeping with
dreams."(2)

Via the amygdala, pontine cells can generate
anxiety, initiating the common nightmare of being pursued but not being able to run, by
sending strong signals to the cerebral cortex, where sensate impressions and memories
would normally meet, but are now hampered by the dearth of amines. With this in mind,
a leading investigator in the field wrote that "dreams are the product of our
cortex's efforts to do the best it can under very difficult circumstances."

(3)

Ironically,

while working on this trace of the journey, I wasn't able to remember my
dreams, even if I tried at the moment of waking up. Something usual for me. I knew that I
had dreamed, but of what I couldn't recall. Then impressions formed while awake began to
substitute for dreams. Thus I arrived at a place dreamed as
if I were still dreaming. Chuang-tzu's butterfly, or Psyche's honey?